Chapter 14 is where we make a really important structural element; the wing spar. This is actually a fairly simple chapter but the layups can be rather long. Good preparation before starting goes a long way towards success.
Start date for this chapter: December 12, 2008



Cutting out the parts from the urethane and pvc foam: no pictures.

All the parts have been cut out, now I am mounting the soft urethane top to the rear foam. This is an easy assembly to keep square; assuming that your jig and table are square that is.

Just another picture from the other side.

Just a picture to show the thinned section at the end. In my opinion, the manual doesn't make it sufficiently explicit which  part of the urethane (top or bottom) receives which reduced section. It can be figiured out from the manual but it could be a lot more explicit. The top part of the wing spar receives the "thicker" thinned down end section.

Putting on the bottom urethane foam for the wing spar. It is very important to get this absolutely square (vertical). This point is not at all emphasized in the manual. With these sticks on the jig, it is not at all evident that you will get consistent results. I took the time to verify that each one was square and then epoxied it in place in addition to the usual screws.

Just another picture of the bottom urethane being installed.

The famous inside layups. What a pain in the #?! Getting the fiberglass to lay down properly whilst respecting the fiber angles was a real bear. I had thought about doing it in two layups as other builders have done but in the end I did it in a single layup. The only thing that didn't get put in a single layup was the square braces which came a day later. In the end, I used a nice little jig made by Jean-Pierre to put the fiberglass into the spar channel without upsetting the fibers. I basically wet the fiberglass out with epoxy on some plastic sheeting. I then transferred it to a piece of packing tape coated foam roughly the size of the interior of the spar box, being careful to fold the sides over onto the top of the carrying foam. I then carried it all over and gently placed it in the spar box and gently pulled up the fiberglass which was then placed on the sides. I used small nails to hold the fiberglass on the vertical faces. A very long layup. It took me 7 hours. You can see the CS4 sections for the front of the wing spar behind the jig, ready to be put in place.
Here are the results after curing for a day. No real problems, no delaminations were found after a very thorough check.
You can see in this picture that I have also applied the fiberglass to CS4 by the dark diagonal green strip after the "break".
Another picture of one of the braces. In a real dufus maneuver, I forgot to put the 3rd brace in the center before applying the leading edge face of the wing spar box. I will put this in later after I make the giant cutouts for the center front of the wing spar box.
Here I am putting on the forward face of the wing spar box. I have used all of my clamps and all of the weight that I could find. I used some flat sheets of wood to avoid bending the forward face down. It was still a bear to make sure that the edges of the wing spar box top and bottom met the forward face of the wing spar box. When I started removing material for the spar cap, I found that there were some regions which had not been in good contact.
A view of the other side.
All the clamps have been removed.
The spar cap cutouts have been made top and bottom. These are absolutely critical and I am going to verify one final time before putting in the shear webs that they are the correct height. It seems that the problem is usually to high and not to low.
I have also been sure to put on 45° marks for the shear web. I have also applied the protective newspaper and tape.
It is impossible to resist the temptation to see if the spar fits in the fuselage. Very encouraging, it fits!!!